April 14 is when Microsoft will stop offering what it calls mainstream support for XP, which includes free security updates and bug fixes for those running retail versions of the eight-year-old operating system. After that date, XP users will have to pay for support on a per-incident basis for bug fixes, although Microsoft will still deliver XP security updates for free until 2014. Microsoft, for its part, says it's well aware that XP is still popular. "Hundreds of millions of Windows XP users are fans of the operating system, and many depend on Windows XP to run legacy applications and hardware not yet compatible with Windows Vista. Even though we're retiring Windows XP, we won't leave you hanging," the company says in a Web site called "Windows XP: The Facts About The Future."